The disclosure of the following priority applications are incorporated herein by reference: Japanese Patent Applications, No. 2000-233831 filed on Aug. 2, 2000 and No. 2000-239531 filed on Aug. 8, 2000.
The present invention relates to a shake detection device that detects vibration due to a shake or the like in an optical device such as binoculars and in a shooting device such as a camera and relates to an optical device, a camera system, and a interchangeable lens in each of which the shake detection device is built.
FIG. 12 is a block diagram illustrating a basic configuration of a blur correction device including a shake detection device. Referring to the Figure, the mechanism of the blur correction device will be described.
Angular velocity sensor 10 is a sensor that first detects a shake to which a camera is subjected. Typically, angular velocity sensor 10 is implemented utilizing a piezoelectric oscillation-type angular velocity sensor that detects Coriolis force. An output from angular velocity sensor 10 is transmitted to reference value calculator 52. Reference value calculator 52 is a unit that calculates a reference shake value using the output from angular velocity sensor 10. Thereafter, the reference shake value is subtracted from a shake signal from angular velocity sensor 10, and then the remainder is transmitted to integrator 54. Integrator 54 is a unit that time-integrates a shake signal expressed in the angular velocity unit to convert it into a shake angle of a camera.
Target drive position calculator 56 calculates target drive position information for driving blur correction lens 80, by adding information such as the focal length of the camera lens to the shake angle information sent from integrator 54.
Drive signal calculator 58, in order to move blur correction lens 80 in response to the target drive position information sent from target drive position calculator 56, calculates a differential between the target drive position information and the present position information of blur correction lens 80 and then supplies a drive current to coil 73.
Actuator 70 is provided to move blur correction lens 80 and is constituted of yoke 71, magnet 72, coil 73, etc. Coil 73 is positioned within a magnetic circuit formed by yoke 71 and magnet 72, and thus when an electric current is supplied to coil 73, a force is generated in actuator 70 in accordance with the Fleming""s left-hand rule.
As shown in FIG. 12, coil 73 is attached to lens barrel 82, which accommodates blur correction lens 80. Because blur correction lens 80 and lens barrel 82 are configured so that they can move perpendicularly to the optical axis I, blur correction lens 80 can be driven perpendicularly to the optical axis I by supplying an electric current to coil 73.
Optical position detector 74 is provided to monitor the movement of blur correction lens 80 and is constituted of infrared ray emitting diode (hereinafter, IRED) 75, slit plate 76, slit 76A, PSD (position sensitive device) 77, etc. A light ray from IRED 75 first passes through slit 76A with the width of the light ray being thus diminished and then reaches PSD 77. PSD 77 is a device that outputs a signal indicative of a light position on its light-receiving surface.
Because slit plate 76 is attached to lens barrel 82 as shown in FIG. 12, the movement of blur correction lens 80 provides the movement of slit 76A, inducing thus the movement of the light ray on the light-receiving surface of PSD 77. Therefore, the position of the light ray on the light-receiving surface of PSD 77 is equivalent to the position of blur correction lens 80. A signal detected by PSD 77 is fed back as position signal 78.
Such a blur correction device is built mainly in a shooting device such as a camera and in an optical device such as binoculars. When those devices are used while being held with a user""s hands, the blur correction device effectively works for correcting image blurring due to a shake from the user. However, the blur correction device need not be operated when the optical devices are fixed, e.g., when they are fixed on a tripod or the like.
The reason why the blur correction device need not be operated in such a situation is that if it is operated, higher power consumption results, the blur correction device unnecessarily operates because of, e.g., noise in the output of the angular velocity sensor, and the image is blurred all the more.
To address those problems, some methods have been proposed to determine whether an optical device with a blur correction device is fixed on a tripod or the like or is held with hands. For example, in Japanese Laid-open Patent Application Hei Nos. 9-304802 and 5-53168 are disclosed methods wherein whether or not the device is fixed is determined by providing a switch on the device""s portion to which a tripod is to be attached.
Also in Japanese Laid-open Patent Application Hei Nos. 10-161172, 11-38461, and 11-64911 are disclosed methods wherein whether or not the device is fixed is determined based on the level or the frequency of the output from the shake detection sensor.
In each category of the patent applications above, when it is determined that the device is fixed on a tripod, a process follows in which blur correction is stopped or the blur correction control is more suppressed than when the device is held with hands.
The above-described prior art determination methods, however, may cause the following problems.
In the case of the first category methods, i.e., where a switch is provided on the device is portion to which a tripod is to be attached, because the switch equally turns to be on either when a tripod is attached to the device or when a unipod is attached to the device, it cannot be identified which of the two is attached.
In other words, attaching a unipod may simply results in recognition of the device being attached with a tripod. When a camera is used being mounted on a unipod, the camera still vibrates due to a shake, although the vibration is decreased a little more than when the camera is supported solely with hands. Thus, blur correction should preferably be done when a camera is mounted on a unipod.
But the first category methods cannot distinguish a tripod from a unipod, and thus being attached with a unipod is recognized as being attached with a tripod, which results in stopping or suppressing the blur correction. Attaching a unipod, therefore, would be susceptible to image blurring.
Moreover, when, not using a tripod or the like, a camera is fixed with the camera being mounted on a base, the methods cannot determine the supporting condition, and thus blur correction is performed even if the camera itself is not vibrating, which results in losing valuable power or in image blurring all the more.
In the case of the second category methods, wherein determination is made by monitoring outputs (amplitude, frequency, etc.) from the shake detection sensor, it may be determined whether the camera is attached to a unipod or to a tripod, through some ingenuities applied to the methods. However, such methods may err in the determination if the sensor is subjected to certain large disturbances.
Illustratively, when the blur correction device is started while the camera is kept in a state of being fixed on a tripod, the device determines that the camera is fixed on the tripod. Notably, however, operations such as a mirror flipping up and down operation, a shutter curtain running operation, and a motor driving operation, which produce vibration of the camera itself, are performed during the camera""s shooting operation. Because the shake detection sensor then also detects the vibration, it is well conceivable that the output amplitude of the shake detection sensor becomes larger during the shooting operation. Thus, even when the camera is fixed on a tripod, it is determined that the camera is held with hands because of the vibration generated during the shooting operation, and the blur correction operation will be initiated. Even in this case, if the output from the shake detection sensor is stable (i.e., not drifting), it is not so problematic; however, if unstable (drifting), the quality of a resultant picture deteriorates.
As described above, with the method wherein a switch is provided on the camera""s portion to which a tripod is to be attached, a tripod cannot be distinguished from a unipod; and with the method wherein the outputs of the shake detection sensor are used, erroneous determination results from the camera""s internal vibration.
Additionally, the following problems may arise.
(a) In the case of determining the supporting condition based only on the frequency or level of the sensor""s outputs, if the shake happens to come to be small while the camera is held with hands, then it may be erroneously determined that the camera is fixed on a tripod. Because an optical device with a built-in blur correction function is considered, by its nature, to be generally used being held with hands, frequent occurrence of such determination is undesirable.
(b) Apropos, the output of an angular velocity sensor includes drift components (i.e., although the sensor is completely stationary, the output varies). For this reason, when the blur correction device is started with the camera being fixed on a tripod or the like, the blur correction lens unnecessarily moves because of the drift components, and the resultant image may deteriorate all the more. Such drift increases especially immediately after power is supplied to the sensor; accordingly, if the camera is fixed on a tripod or the like, it should be promptly recognized that the camera is so fixed. However, when the supporting condition is determined based on the frequency or level of the sensor""s outputs, a certain amount of time is inevitably required before determining the condition because the frequencies of a shake from a user range mainly from 3 to 5 Hz.
(c) Even when the camera is fixed on a tripod, the camera may be panned to adjust the composition. In that case, although determining during the panning that the camera is held with hands is acceptable, the determination should be returned, on completion of the panning, to the determination indicating that the camera is fixed. However, if the determination is made to return too easily, the situation described in (a) above, wherein although the camera is held with hands, it is erroneously determined that the camera is fixed, may occur more frequently.
Therefore, there have been the following needs: to realize both precise shake detection and power savings without being affected by the fixation method differences and internal vibrations; and to, by effectively determining whether the optical or shooting device is fixed or is held with hands, realize shake detection and/or blur correction that do not irritate the user whether the device is held with hands or is mounted on a tripod.
According to the present invention, in order to address those needs, when an optical or shooting device including the shake detection device performs an operation that generates vibration of the optical or shooting device itself, the determination of the fixation condition is halted even when the shake is being detected. Further, the shake detection device stores the determination result of the fixation condition at the time when the fixation condition determination halt was initiated. Further, assuming that the optical or shooting device including the shake detection device is a camera, there are, as the operation that generates vibration of the camera itself, operations such as the film winding operation, the shutter operation, and the mirror driving operation; and, when at least one of those operation is performed, the determination of the fixation condition is halted.
According to another aspect of the present invention, as a supporting condition determination portion (fixation condition determination portion) for determining whether the device is in a state of stably supported condition (fixed) or is in a state of non-stably supported condition (held with hands), a stable support condition detection portion and a non-stable support condition detection portion are separately provided. Further, with the supporting condition determination portion, stable support condition detecting and non-stable support condition detecting are performed alternately and successively.
Still further, the stable support condition detection time duration is made smaller than the non-stable support condition detection time duration. In addition, by regarding the initial stage of the vibration detection as in a stabilized state in consideration of the unstableness of the stage, false detection of the initial stage of the vibration detection as in a non-stabilized state can be avoided.